Instrument for use in determining the stress in an electrodeposit



Sept. 25, 1951 BRENNER 2,568,713

INSTRUMENT FOR USE IN DETERMINING THE STRESS IN AN ELECTRODEPOSIT Filed April 6, 1949 2 Sheets-Sheet 1 4 Z N 2 4 R 5 7 0 RE 2 2 mm 1mm: o 5 P W W I 5 I 2 1| 6 z 4 4 a 9. w z w W 0 a 4 2 4 1 3 I 4 W z a F/ w -LMM 4 0 ATTORNEY Sept. 25, 1951 A. BRENNER 2,568,713

INSTRUMENT FOR USE IN DETERMINING THE STRESS IN AN ELECTRODEPOSIT 2 Sheets-Sheet 2 Filed April 6, 1949 INVENTOR ABA/ER BRENNER Patenteci Sept. 25, 1951 INSTRUMENT FOR USE IN DETERMINING THE STRESS IN AN ELECTRODEPOSIT Abner Brenner, Chevy Chase, Md., assig'nor to the United States of America as represented by the Secretary of Commerce Application April 6, 1949, Serial No. 85,922 4 Claims. (01. 73-150) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 1 The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment to me of any royalty thereond sleeve 20 while my helix I I is adapted to telescopically fit over the sleeve 22 and to be detachably secured thereto by a clamping sleeve 23 provided with a. bolt 24 which also serves to elecon in accordance with the provisions of the act trically connect my helix H with an insulated of April 30, 1928 (ch. 460, 45 Stat. L. 467).

My inventionrelates to a novel apparatus for measuring stress in the electrodeposits by means of the deformation of a helix accompanying the electroplating of said helix with the same or different metal; and particularly to an apparatus which visually registers an increase in deformation during the deposition of the coating. An essential element of my apparatus is a metal helix coated on one cylindrical surface with a suitable varnish which inhibits the electrodeposition of metal upon said surface, while the opposite surface is clean and suitable for receiving an electrodeposited coating.

The electrodeposition of metal on only one cylindrical surface of the metal helix is accompanied by a progressively increasing deformation of the helix which produces a change in the radius of curvature of the helix, and my apparatus is designed to multiply this change and to visually register this movement by an indicating pointer pivoted over a graduated dial face.

In the accompanying drawings which illustrate a preferred form of my invention:

Figure 1 is an axial section of my apparatus.

Figure 2 is a side elevation of a helix'used in my apparatus.

Figure 3 is a plan of a pinion, segmental gear, and calibrated disc which serve to magnify the distortion of my helix during an electroplating operation.

Figure 4 is a section on the line 4-4 of Figure 1.

In these drawings:

A metallic helix H (Figure 2) is coated on the inner cylindrical surface with a suitable varnish which serves to prevent the electrodeposition of metal upon said coated surface. Preferably, this helix is formed by winding a strip of base metal around a cylindrical mandrel annealing the helix,

and then removing the helix from the mandrel.

sleeve 19 and helix ll.

28 is fastened an arm 3| having a terminal segmental gear 32, which meshes with a pinion 33 mounted in adjustable bearings 34. To the pinion 33 is rigidly secured a pointer 35 which is adapted to move over a scale 36 on the plate 26. A cen- 20 trally apertured insulating plug 31 is adapted to be clamped to the rod 21 by a set screw 38 and is provided with one or more fluid passages 39. A second clamping sleeve 40 provided with a clamping bolt 4| serves to transmit motion from 25 my helix ll through the plug 31, rod 21, and gear 32 to the pinion 33, and the attached pointer 35. The bearings 34 are mounted in a suitable U-shaped support 42 which is riveted or otherwise fastened to the plate 26. The pointer 35 is provided with a cdunterbalancing weight 43.

The radii of the segmental gear 32 and the pinion 33 are so proportioned as to give a tenfold magnification of the angular displacement of the rod 21. The sleeve l9 does not make electrical contact with the helix ll while the clamps 23 and 40 attach the helix II to the remainder of the apparatus. These clamps also serve as electrical guards which give a very uniform current distribution over the active surface of the helix ll. Loosening the clamping bolt 29 permits sliding the rod 21 within the sleeve 28, while loosening the knurled bolt 2| permits adjusting shouldered sleeve with respect to other elements of the framework l3.

By relative rotation of the sleeve 20 with respect to the sleeve I9, the pointer 35 may be set at any desired graduation on the dial of the plate 26 and clamped by the bolt 2|.

The entire assembly is suspendedby the hook [5 within a tank (not shown) containing a suit- 53 negative lead to the conducting wire 25, my apparatus is ready to start plating on the helix ll. Since the top of the helix H is firmly secured to the suspending framework 13, the bottom only of the helix H is free to turn as the plating proceeds, which motion is transmitted through the rod 21 and multiplying gearing to the pointer 35.

Between successive tests only the helix and attaching clamps need to be disconnected from the remainder of the assembled apparatus. After the weight and/or thickness of the coating has been determined the electrodeposit may be stripped from the helix by a suitable chemical I solvent.

The plate 26 and the entire registering mechanism may be enclosed in a protective transparent case (not shown).

If coatings of the same thickness are deposited upon the helix, the deflection of the pointer can be taken as a relative measure of the stress existing in the coatings. In some studies of stress in deposits, only the relative value of stress was determined, but it is preferable to state the stress in absolute values in order that the work of different investigators can be compared.

In order to calculate the stress in the deposit from the deflection of the pointer, one must also know the thickness of the coating and the force constant and dimensions of the helix. The constant K of the helix is determined by applying a known torque to the helix and noting the deflection of the pointer. The torque is most easily applied by suspending a known weight from the arm of the gear segment, via a pulley and thread.

woight (in 1b.) Xdistance to pivot (inches) K degrees deflection 2K D ptd Stress in coating (lb/in.

The pitch of the helix is measured with a rule. 'I he thickness of the helix strip is measured with a micrometer. The thickness of the electrodeposit is calculated from the weight of coating deposited upon the helix.

The calculation of the stress is simplified by first determining the deflection constant of the helix, that is, the torque required to cause a deflectionof one degree. This can be done by attaching a thread to the arm 3| near the gear 32 and passing it over a removable pulley, then with the helix clamped with the pointer at a selected point of the dial, weights are attached to the string and the deflections of the pointer 35 noted. An initial load of to g. may be attached to the string and then as weights are added, recording the increased deflections. By measuring the distance from the ax s of the torque rod to the point of attachment of the string on the arm 3| and using the recorded load in grams, a. deflection constant may be calculated which shows the relation of the bending movement of the helix to the degrees of deflection.

My apparatus provides a means for investigating the variations in stresses due to variations in the conditions of deposition and to differences in the thickness of the deposits and differences a jurious deformations due to stresses which may result in visual failures such as the peeling, blistering or cracking of the deposited coating, which failures render the base metal more susceptible to corrosion.

My apparatus provides a means for Zregister ing stress deformations in a coating while it is being deposited and thereby aids in production control and in the improvement of the quality of the plating on articles. It is rugged, easily operated, self-contained, and comparatively inexpensive.

It should be understood that the present disclosure is for the purpose of illustration only, and that the invention includes all modifications and equivalents which fall Within the scope of the appended claims.

What I claim is:

1. An instrument for measuring the stress in an electrodeposit, which comprises a metallic helix having on one cylindrical surface a depositinhibiting film, on the other a clean surface for receiving an electrodeposit, a suspending framework, a clamping sleeve provided with a suitable electrical terminal for detachably securing said helix to said framework, a rod rotatably mounted in the axis of said framework, a segmental gear secured to the upper end of said rod, a pinion with a pointer supported by said framework and meshing with said gear, an insulating plug clamped to the lower end of said rod, and a second helix clamping sleeve for compressing the lower end of the helix against said plug for transmitting torque due to a deformation of said helix through said plug and said rod to said pointer.

2. An instrument for indicating stress in an electrodeposit during the course of the deposition thereon, comprising a metallic helix having on one cylindrical surface only a deposit-inhibiting film, an electrical terminal at one end of said helix, a suspending framework, means for detachably suspending said helix from said framework, a rod rotatably mounted in the axis of said framework, a segmental gear secured to the upper end of said rod and non-rotatably connected therewith, a pinion supported by said framework and meshing with said gear, and means for transmitting torque to said rod from the lower end of said helix.

3. An instrument for use in determining the stress in an electrodeposit which comprises a metallic helix having on one cylindrical surface only a deposit-inhibiting film, a suitable suspending framework, a clamping sleeve provided with an electrical terminal for detachably suspending said helix from said framework, a rod rotatably mounted in the axis of said framework, a segmental gear secured to the upper end of said rod, a pinion with a rigidly connected pointer supported by said framework and meshing with said gear, an insulating plug clamped to the lower end of said rod, a second helix clamping sleeve for compressing the lower end of the helix against said plug, whereby torque due to any deformation of said helix will be transmitted through said plug and said rod to said pointer.

4. An instrument for use in determining the stress in an electrodeposit during the deposition of a metallic coating on a metal base, comprising a metallic helix having one deposit-receiving cylindrical surface and an opposite surface pro tected by a deposit-inhibiting film, a helix clamping sleeve provided with an electric terminal, a suspending framework provided with a depending tubular portion, an insulating sleeve on said tubular portion against which said helix is clamped by said clamping sleeve, a lower insulating plug within the helix provided with a longitudinal aperture for a rod, a lower clamping sleeve for compressing said helix against said plug. a torque transmitting rod within said sleeve non-rotatably connected with said p1ug,'a revoluble motion multiplying means operatively coupled with said torque-transmitting rod, and an indicator for registering said multiplied mo- 1 tion.

ABNER BRENNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

